Hi everyone,I'm one of those "deviants" (or some might say stubborn old-fashioned dudes maybe?) who tried FSX on Win7-64 for 3 days and after reading the problems in these forums, realized it was a waste of time and installed FSX on Win XP Pro 32-bit. I do not have WinXP 64 so I did not have any other choice. I have a dual-boot system (WinXP, Win7), so I can use both. But I have uninstalled FSX from Win7 for now at least...I have a question regarding the /3GB switch which I can't quite find by searching these forums: I currently have only a 256MB video card (see my signature) but plan to upgrade to a 1GB card in the near future. What will happen to the memory available to WinXP OS after switching to a 1GB video card from a 256MB one? I currently have success with the " /3GB /userva=2560 " switch. I don't have many add-ons yet. A few free airports sceneries and just yesterday, I purchased the PMDG 744X. The Jumbo runs great now, after a few test flights. I plan to add more stuff with time, mainly airport sceneries like Cloud 9 Amsterdam for FSX (I am a former FS2004 user and had this scenery there also), FSGenesis mesh ... etc.But will having a 1GB video card starve the OS of memory? If I understand correctly, the OS will still use up to the 4GB limit (I have XP SP3 by the way), so that will leave only 512 MB I think, for the OS if I continue to use the 2560 as the size, is this right?John

Hello256MB /userva=3072 (ie, 3GB)512MB /userva=2816768MB /userva=25601024MB /userva=2304

Hello256MB /userva=3072 (ie, 3GB)512MB /userva=2816768MB /userva=25601024MB /userva=2304

I'm also just switched from 320MB card to 1GB but I'm not aware to any necessary changes/additions to the cfg file. Cna yoy please elaborate (or just direct me to another link) this issue.Thanks,Shayt

Hello256MB /userva=3072 (ie, 3GB)512MB /userva=2816768MB /userva=25601024MB /userva=2304

Thank-you Mad Dog. This is good to know.

I'm also just switched from 320MB card to 1GB but I'm not aware to any necessary changes/additions to the cfg file. Cna yoy please elaborate (or just direct me to another link) this issue.Thanks,Shayt

Shayt,This is to for the FSX.CFG file, it is actually a command in the Windows XP BOOT.INI file. If you search this forum with this keyword "/3GB switch" or just /3GB, you'll find more details. Basically, it is giving MORE virtual (pagefile) memory for applications BEYOND the 2GB limit imposed by 32-bit Windows XP (or any 32-bit OS including Vista 32). Please anyone correct me if I'm wrong, but that was my understanding from what I've read about this switch. Here is an example of my boot.ini. NOTE that there are TWO separate operating system entries in case you experience boot failure of other issues when using this switch. One entry is the standard Windows XP entry, the second one which also shows up in the boot menu, is the one for this 3GB switch:[operating systems]multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows XP Professional" /FASTDETECTmulti(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows XP PRO 3GB switch" /FASTDETECT /3GB /userva=2560The boot.ini is a hidden system file so you have to select the show hidden files option and the show system files option in windows explorer tools menu. Note that I had set 2560MB and will have to probably change this to 3072 MB (or 3GB) based on maddog's recommendations.Hope this helps.John

Hi everyone,I'm one of those "deviants" (or some might say stubborn old-fashioned dudes maybe?) who tried FSX on Win7-64 for 3 days and after reading the problems in these forums, realized it was a waste of time and installed FSX on Win XP Pro 32-bit. I do not have WinXP 64 so I did not have any other choice. I have a dual-boot system (WinXP, Win7), so I can use both. But I have uninstalled FSX from Win7 for now at least...I have a question regarding the /3GB switch which I can't quite find by searching these forums: I currently have only a 256MB video card (see my signature) but plan to upgrade to a 1GB card in the near future. What will happen to the memory available to WinXP OS after switching to a 1GB video card from a 256MB one? I currently have success with the " /3GB /userva=2560 " switch. I don't have many add-ons yet. A few free airports sceneries and just yesterday, I purchased the PMDG 744X. The Jumbo runs great now, after a few test flights. I plan to add more stuff with time, mainly airport sceneries like Cloud 9 Amsterdam for FSX (I am a former FS2004 user and had this scenery there also), FSGenesis mesh ... etc.But will having a 1GB video card starve the OS of memory? If I understand correctly, the OS will still use up to the 4GB limit (I have XP SP3 by the way), so that will leave only 512 MB I think, for the OS if I continue to use the 2560 as the size, is this right?John

Yes it will count against your /3GB switch. I have two 768MB Nvidia cards and they counted against my 4GB of memory so I had to use the USERVA=2560 switch (as Maddog has already stated). The USERVA switch is for Vista and Windows 7 32 bit OS's only. You don't need it for 64 bit systems, including WinXP 64 bit systems. The /3GB switch is only used in WinXP 32 bit systems. You can use the keyword box to search this forum for /3GB or OOM and you should get hundreds of hits on this subject. Or you can visit NickN's thread at the following link: http://www.simforums.com/forums/forum_posts.asp?TID=29041.Best regards,Jim

Basically, it is giving MORE virtual (pagefile) memory for applications BEYOND the 2GB limit imposed by 32-bit Windows XP (or any 32-bit OS including Vista 32). Please anyone correct me if I'm wrong, but that was my understanding from what I've read about this switch.

Excellent presentation up to this point...This has nothing whatever to do with either "virtual (pagefile) memory" or physical RAM.It has everything to do with Virtual Address Space. Every program running has its own, unique VAS table, the size of which is preset unless otherwise reallocated through use of the /3GB switch and /userva= size specification.At any given time there will be many VAS tables in existence. It might help to think of VAS tables as a table-of-contents. A VAS table is not the data, but rather a list of addresses where the data may be found.Unlike a book's table-of-contents which remains fixed and immutable, a VAS table's index is dynamic. It is a "snapshot" of where data existed in physical RAM before it was shuffled of to short-term storage in Virtual RAM. When it's time to load the application back into physical RAM, the VAS table provides the addresses needed to re-load it precisely where it was before... :( For FSX, the wheels fall off the wagon if FSX needs to write some data and it cannot find a 1MB contiguous block of currently un-used VAS addresses. That is the entire reason for increasing the size of the available VAS table. While it will not completely eliminate the possibility of such an event occurring, it will greatly decrease the probablility... :(

It has everything to do with Virtual Address Space. Every program running has its own, unique VAS table, the size of which is preset unless otherwise reallocated through use of the /3GB switch and /userva= size specification.

Bill, this is interesting reading.. but you did not comment on whether the USERVA size should be changed with different size video cards :(

Bill, this is interesting reading.. but you did not comment on whether the USERVA size should be changed with different size video cards :(

No I did not, quite deliberately. I didn't want to muddy the waters any further, but rather address the single point regarding just what VAS actually is......and is not.In my Wiki article and uncounted other posts I have mentioned that any increase in VRAM will affect the size of /userva that can be reallocated to application's VAS tables. (note the plural)It's a case of robbing Peter to pay Paul. Double your card's VRAM size and you must decrease the /userva allocation accordingly.

Fr Bill is spot on with his take on VAS.This is from MS: http://support.microsoft.com/kb/940105"On a modern operating system such as Windows Vista, applications run within their own private virtual address space. Typically, the size of the virtual address space is fixed at 2 gigabytes (GB) for 32-bit applications. How much virtual address space is available is not related to how much physical memory there is on the computer." and more importantly:"A modern graphics processing unit (GPU) can have 512 MB or more of video memory. Applications that try to take advantage of such large amounts of video memory can use a large proportion of their virtual address space for an in-memory copy of their video resources. Applications that try to take advantage of such large amounts of video memory can use a large proportion of their virtual address space for an in-memory copy of their video resources. On 32-bit systems, such applications may consume all the available virtual address space. "The solution - switch to a 64-bit OS and this becomes academic.It should also be noted that in some cases the /3GB (and/or /USERVA) switch can cause serious operating problems with other software running under Windows 32-bit - it is a band-aid at best.The other thing to remember is that Vista and Win 7 handle video memory much better than WinXP. In the latter it is utilised on a first come first served basis, so if you have opened a graphics hungry application before FSX you may run more readily into the dreaded OOM issues.RegardsPeterH

Fr Bill is spot on with his take on VAS.This is from MS: http://support.microsoft.com/kb/940105"On a modern operating system such as Windows Vista, applications run within their own private virtual address space. Typically, the size of the virtual address space is fixed at 2 gigabytes (GB) for 32-bit applications. How much virtual address space is available is not related to how much physical memory there is on the computer." and more importantly:"A modern graphics processing unit (GPU) can have 512 MB or more of video memory. Applications that try to take advantage of such large amounts of video memory can use a large proportion of their virtual address space for an in-memory copy of their video resources. Applications that try to take advantage of such large amounts of video memory can use a large proportion of their virtual address space for an in-memory copy of their video resources. On 32-bit systems, such applications may consume all the available virtual address space. "The solution - switch to a 64-bit OS and this becomes academic.It should also be noted that in some cases the /3GB (and/or /USERVA) switch can cause serious operating problems with other software running under Windows 32-bit - it is a band-aid at best.The other thing to remember is that Vista and Win 7 handle video memory much better than WinXP. In the latter it is utilised on a first come first served basis, so if you have opened a graphics hungry application before FSX you may run more readily into the dreaded OOM issues.RegardsPeterH

Thank-you once again PeterH, Fr. Bill and Jim. Since I will boot XP with the 3GB switch only when running FSX and will not necessarily use this option when running other programs (if I need them, since I do have a dual-boot PC with Win7-64 and will try to run my other apps like Pinnacle Studio 12 for video, Corel PaintShop Pro X2 for photos, from Win 7. These apps are compatible with Win 7 though I have not tested Studio yet. However, when running FSX, I will eventually be running other independent apps, like a weather app like ASV, and VATSIM pilot software such as Squawkbox and vroute, and a fuel planner (which I will close after using) like the PMDG fuel planner or others. I assume you have run these apps or similar ones with using FSX in WinXP 32, before you used Vista or 7. Can you tell me if they are stable and run properly? I assume that they will, but when using add-ons such as PMDG (I already have their 744X for FSX) and several add-on sceneries like aiports, possibly cities and FSGenesis or FSGlobal mesh, then what happens with VAS in WinXP 32-bit? Do you get OOMs? ... If I could find WinXP 64-bit, I'd buy it but for now, I have not really looked. But definitely will not be trying my Win7-64 until possibly, there are some updates by Microsoft to address its issues (an SP1 perhaps?). By the way, along these lines, yesterday, my Windows 7 updates notified me of new updates. I verified ONE of them and it addresses application compatibility issues where apps run in VISTA compatibility mode in Win7 instead of Win7 mode. One of the apps in the list was FS2004 (no FSX mentioned...) Have you seen these updates in your Win 7 automatic updates, ready to install, or have you already installed them? Feb. 24 was when I got the notification so you can check in your systems. Another appl. was Pinnacle Studio 12. There were also many many games, designed for older version of Windows in the list. I will try to find the KB article and post it here. I can't do it now, because I'm in my WinXP. Need to boot into my Win7 for that.Cheerios! (actually, I prefer granola cereals myself! ha!)John

By the way, along these lines, yesterday, my Windows 7 updates notified me of new updates. I verified ONE of them and it addresses application compatibility issues where apps run in VISTA compatibility mode in Win7 instead of Win7 mode. One of the apps in the list was FS2004 (no FSX mentioned...) Have you seen these updates in your Win 7 automatic updates, ready to install, or have you already installed them? Feb. 24 was when I got the notification so you can check in your systems.

Actually I hadn't noticed. I've been running both FS9 and FSX on my new i7 Win7x64 system for months with zero problems... :( ...although I probably shouldn't have written that, what with Murphy being such a persistent fellow... :(

Hello256MB /userva=3072 (ie, 3GB)512MB /userva=2816768MB /userva=25601024MB /userva=2304

I'm curious about the above table, thanks for posting it. I recall I read recommendations here to use 2560 for a 512MB card as a safe value, and that it had to be divisible by 64 etc. It looks like 2816 is the right value for a 512Mb card? Any comments on it, guys?Thanks,Dirk.